Observer, Quorum

This article closes the series for DG and Fast-Start Failover that I covered with more details the case of isolation can leverage the shutdown of your healthy/running primary database. The “ORA-16830: primary isolated from fast-start failover partners”.

In the first article, I wrote about how one simple detail that impacts dramatically the reliability of your MAA environment. Where you put your Observer in DG environment (when Fast-Start Failover is in use) have a core figure in case of outages, and you can face Primary isolation and shutdown. Besides that, there is no clear documentation to base yourself about “pros and cons” to define the correct place for Observer. You read more in my article here.

In the second article, I wrote about one new feature that can help to have more protected and cover more scenarios for Fast-Start Failover/DG. Using Multiple Observers you can remove the single point of failure and allow you to put one Observer in each side of your environment (primary, standby and a third one). You can read more in my article here.

In this last article I discuss how, even using all the features, there is no perfect solution. Another point is discussing here is how (maybe) Oracle can improve that. Below I will show more details that even multiple observers continue to shutdown a healthy primary database. Unfortunately, it is a lot of tech info and is a log thread output. But you can jump directly to the end to see the discussion about how this can be improved.


Observer, More Than One

Recently I made a post about a little issue that I got with Oracle Data Guard. In that scenario, because of outage in the standby datacenter, healthy primary database shutdown with error “ORA-16830: primary isolated…”. Just to remember that the database was running with Maximum Availability, Fail-Start Failover enabled and (the most important detail) the Observer was running in the standby datacenter too.

The point from my previous post tried to show that does not exists one doc that provides full details about “pros” and “cons” where put your observer. Whatever the place, on the primary datacenter or in standby, it has little details to check. Even the best (ideal) scenario, with a third datacenter, can be tough to sustain.

Here I will try to show one option that can help you and improve the reliability of your MAA/DG environment. At least, you will have more options to decide how to protect your database. Bellow, I show some details about how to configure and use multiple observers, but if you want to jump and see a little concern you can directly to the end of the post.


Observer, Where?

Some months ago I got one error with Oracle Data Guard and now I had time to review it again and write this article. Just to be clear since the begin, the discussion here it is not about the error itself, but about the circumstances that generated it.

The environment described here follow, at least, the most common best practices for DG by Oracle. Have 1 dedicated server for each one: Primary Database, Physical Standby Database and Observer. The primary and standby resides in different datacenters in different cities, dedicated network for interconnect between sites, protection mode was Maximum Availability and runs with Fast-Start Failover enabled (with 30 seconds for threshold). The version here is 12.2, but will be the same for 19c. So, nothing so bad in the environment, basic DG configuration trying to follow the best practices.


Oracle e MAA – Artigo VIII – Fast-Start Failover

Depois de configurar o Broker, precisamos de um último passo para garantir que os requisitos básicos do MAA estejam contemplados. Nos últimos artigos passamos por alguns passos que provavelmente você não iria realizar em produção (e nem gostaria), fizemos o failover e o switchover (ambos com o broker – que configuramos aqui).


Neste artigo vamos configurar/adicionar ao ambiente a figura do Observer, será habilitado o Fast-Start Failover (FSFO) no Broker para permitir um monitoramento em tempo real do ambiente. Com isso, em uma eventual falha do ambiente primary o standby irá assumir o papel sem ser necessário executar qualquer comando.

Continue lendo…